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The Other Animation Principles Of Motion: Newton's Laws of Motion

After discussing timing and spacing, I think it's a little easier to see how all of these animation principles really feed off of each other and overlap in many ways. So instead of focusing on them as separate principles, I decided to discuss the remaining motion principles as a group. They really are artistic definitions of scientific principles, a way for us to discuss and push reality while still basing our animation on realistic physics to ground our work and make it more believable. Starting with reality, we can look at science, then we will define and apply the animation principles.

Obviously, I'm not a scientist so I will not try to get too technical, but I think it's helpful to look at the reality of motion. Specifically Newton's 3 Laws of Motion:

(1)

  • Every object in a state of uniform motion will remain in that state of motion unless an external force acts on it
  • (objects at rest will stay at rest until another force acts upon it, objects in motion will stay in motion until another force acts upon it)
  • (2)
  • Force equals mass times acceleration Fm x a 
  • (lighter objects need less force to start moving and accelerate faster than heavy objects which need more force to start moving)
  • (3)
  • For every action, there is an equal and opposite reaction
  • (A wall applies the same amount of force to your hand but in the opposite direction that you are pressing the wall)



This may be a little confusing so let's apply these ideas to an example. How about a leaf. You thought I was going to say bouncing ball didn't you, well we could, but I want to try the leaf because you can find the ball example most places if you haven't already.

So we have a leaf, a big hosta leaf. It is very happy as part of the hosta plant resting with a slight bend as a result of the constant pull of gravity, this is already an interaction of Newton's laws but we'll work from here. 

Now a wind starts to blow and our resting leaf now has an outside force acting on it causing it to move (Newton's First Law). This wind is just a little breeze, and the hosta leaf is large and somewhat sturdy as leaves go and therefore the leaf reacts slowly and only moves slightly (Newton's Second Law; Easing, Squash, Arcs). When the light breeze passes, the strong stem of the hosta leaf that has been pushing against the wind is now able to apply more force than the breeze, causing the hosta leaf to swing back and return to a state of rest (Newton's Third Law; Easing, Stretch, Follow Through, Arcs).

All animation, no matter what style, applies these laws in varying degrees. And notice how quickly they blend, interact and overlap with each other. If only we had a way to talk about specific aspects of the motion to better communicate our ideas...oh wait, we do! Our animation principles! First, we need to introduce and define them.

In animation, we communicate these laws with the principles of Anticipation, Squash & Stretch, Slow-In & Slow-Out (Easing), Follow Through, Secondary Action, and Arcs. Here is a brief explanation of these terms:

Anticipation - An action that prepares the viewer for the action that is about to happen

Squash & Stretch - The distortion of a character or object's base shape to show its elasticity, force, and resistance to other forces

Slow-In & Slow-Out (Easing) - The gradual increase or decreasing of movement through space between sequential images

Follow Through - The drag or overlapping action of materials, mass, and/or appendages that are reacting to outside forces or the driving force of a character or object

Secondary Action - An action that supports the overall movement and idea of the main action taking place

Arcs - The appealing and believable path of motion that organic objects follow

While it is important to try and understand their differences, don't forget how they are connected in the process. The animation principles give us a verbal way to communicate what needs to happen visually in motion and by exaggerating things like squash and stretch, slow-in, slow-out, etc. we can better communicate the feeling behind the motion to the audience.

Here is our leaf again but this time the action is described with our animation principles.

In the example above we looked at a leaf, one without life or personality. It was being motivated to move by an external force, the wind. While these principles apply there is a deeper application that I feel often gets overlooked when explaining the principles. The deeper application is using these principles to express not simply "observed motion" but "visual emotion".

When animating characters, or objects with personality, it is extremely important to consider both the external and internal forces acting on them. Why are they doing what they are doing? Realize that the character's motivation is a force acting on them, and just like an external force, it will affect how the character moves, and we can use these same principles to help both describe the movement and visually communicate what they are feeling. To explore this a little further, I'm going to analyze the "eye-roll" animation from the second timing and spacing post.

If you remember the premise, a teenager that was about to get lectured on a topic that he had been lectured on many times before, and from a simple summary like this we can discover the attitudes and motivations for the character. The teen is probably in a hurry to meet with friends or is maybe returning late from being with friends when they are stopped for this lecture. They are thinking things like, "I know what you're going to say", "this again...", and "OMG!" probably all at the same time because this lecturer is so old and slow! They are annoyed and to show their annoyance, they take a long slow breath for a big dramatic sigh, and a dramatic eye-roll just in case you don't get the hint from the sigh. These are the internal forces driving the actions and acting of the character.

Here is how these principles can help visually communicate these internal forces. To anticipate the big deep breath, the character drops their head slightly just before starting to inhale, which also gives a squash to the overall silhouette of the character. Likewise, their eyes and mouth close to squash before they stretch open. The head slows-in to its pose as the character's lungs fill, the silhouette stretches, then the character slows-out of the pose. This easing creates a pause that allows the viewer's eyes to rest on-screen so that the secondary action of the eye-roll is clear. Then the character quickly exhales, dropping their head which follows through after the chest and neck have stopped moving, recovers, and settles into a natural bored pose. The overall motion of the head has followed an arc from screen left, up, and down to lower screen right.


See how helpful it is to be able to communicate actions with words! As helpful as these principles are for teaching ideas, they are even more useful as a common vocabulary. Having these terms allows us to save time by being able to clearly communicate our ideas to each other both before and during animation.

I hope that these examples have been helpful in terms of trying to understand these principles. I have really enjoyed going through them. I would like to make it through all 12 but may take a little break here we will have to see. Thank you again for taking the time to read and I'll have another post again soon!

 

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